On 30 nov. 2009, at 19:34, Anthony Liguori wrote: > Jan Kiszka wrote: >> This series is a larger rework of the block migration support qemu >> recently gained. Besides lots of code refactorings the major changes >> are: >> - Faster restore due to larger block sizes (even if the target disk is >> unallocated) >> - Off-by-one fixes in the block dirty tracking code >> - Allow for multiple migrations (after cancellation or if migrating >> into a backup image) >> - Proper error handling >> - Progress reporting fixes: report to monitor instead of stdout, report >> sum of multiple disks >> - Report disk migration progress via 'info migrate' >> - Progress report during restore >> >> One patch is directly taken from Pierre Riteau queue [1] who happend to >> work on the some topic the last days, two more are derived from his >> commits. >> >> These patches make block migration usable for us. Still, there are two >> more major improvements on my wish/todo list: >> - Respect specified maximum migration downtime (will require tracking >> of the number of dirty blocks + some coordination with ram migration) >> - Do not transfere unallocated disk space (also for raw images, ie. add >> bdrv_is_allocated support for the latter) >> >> In an off-list chat, Liran additionally brought up the topic that RAM >> migration should not start too early so that we avoid re-transmitting >> dirty pages over and over again while the disk image is slowly beamed >> over. >> >> I hope we can join our efforts to resolve the open topics quickly, the >> critical ones ideally before the merge window closes. >> > > That really needs to happen no later than the end of this week. > > So Pierre/Liran, what do you think about Jan's series? > > Regards, > > Anthony Liguori
I'm currently testing these patches. Here are a few issues I noticed, before I forget about them. - "migrate -d -b tcp:dest:port" works, but "migrate -b -d tcp:dest:port" doesn't, although "help migrate" doesn't really specify ordering as important. But anyway I think Liran is working on a new version of the command. - We use bdrv_aio_readv() to read blocks from the disk. This function increments rd_bytes and rd_ops, which are reported by "info blockstats". I don't think this read operations should appear in VM activity, especially if this interface is used by libvirt to report VM stats (and draw graphs in virt-manager, etc.). Same for write stats. - We may need to call bdrv_reset_dirty() _before_ sending the data, to be sure the block is not rewritten in the meantime (maybe it's an issue only with kvm?) - I seem to remember that disk images with 0 size are now possible. I'm afraid we will hit a divide by zero in this case: "progress = completed_sector_sum * 100 / block_mig_state.total_sector_sum;" Apart from that, it works quite fine. Still a few things to cleanup (e.g. unused constants) but much better than before. However, I haven't tested the incremental transfer support at all yet. It's on my todo list. -- Pierre Riteau -- http://perso.univ-rennes1.fr/pierre.riteau/